The I shift is an automated manual gearbox. As with a conventional manual gearbox the i-shift has a main shaft, counter shaft and a splitter for high and low. The truck only has an accelerator pedal and brake pedal- no clutch pedal. The transmission computer (TECU) with sensors, solenoids and actuators does everything the driver used to do.
To check the oil level- the sight glass is located on the left hand side front of the gearbox. Minimum level is the bottom of sight glass. Maximum level is at the top of the sight glass
Fill/top up the oil level through this plug. On some models of i-shift this plug has a breather hose that simply has to be pulled off before removing the plug and filling